// strings/JGrep.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// A very simple version of the "grep" program
// {java JGrep
// WhitherStringBuilder.java 'return|for|String'}

import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class JGrep {
    public static void
    main(String[] args) throws Exception {
        if (args.length < 2) {
            System.out.println(
                    "Usage: java JGrep file regex");
            System.exit(0);
        }
        Pattern p = Pattern.compile(args[1]);
        // Iterate through the lines of the input file:
        int index = 0;
        Matcher m = p.matcher("");
        for (String line :
                Files.readAllLines(Paths.get(args[0]))) {
            m.reset(line);
            while (m.find())
                System.out.println(index++ + ": " +
                        m.group() + ": " + m.start());
        }
    }
}
/* Output:
0: for: 4
1: for: 4
*/
